Conventionally, an industrial robot has been widely used in which a conveying object is conveyed out from an accommodating part which accommodates conveying objects or a conveying object is conveyed into an accommodating part. As this type of an industrial robot, an industrial robot has been known in which a semiconductor wafer, which is a conveying object, is conveyed out from a vacuum chamber, which is an accommodating part, or a semiconductor wafer is conveyed into the vacuum chamber (see, for example, Japanese Patent Laid-Open No. 2000-308988).
The industrial robot which is described in the above-mentioned Patent Reference is incorporated in a manufacturing system for a semiconductor device. A semiconductor wafer is conveyed out by the industrial robot from a load lock chamber (vacuum chamber) into which a semiconductor wafer is conveyed from the outside or the semiconductor wafer is conveyed into a process chamber (vacuum chamber) for performing a predetermined processing on the semiconductor wafer. Further, the industrial robot is disposed in a transfer chamber (vacuum chamber) around which the load lock chamber and the process chamber are disposed.
In recent years, increasing of a conveying speed for a semiconductor wafer has been required in an industrial robot in order to improve productivity. On the other hand, even at a high conveying speed, a semiconductor wafer is required to be held firmly on a hand so as not to occur positional displacement of the semiconductor wafer on the hand on which the semiconductor wafer is placed. In an industrial robot used in the atmosphere, a method in which a semiconductor wafer is held by vacuum suction has been widely utilized but, in an industrial robot disposed in a vacuum chamber, a semiconductor wafer cannot be held by vacuum suction. Therefore, in the above-mentioned Patent Reference, a mechanical clamp mechanism for holding a semiconductor wafer on a hand is proposed as a means for coping with a demand for increasing of a conveying speed.
The clamp mechanism proposed in the Patent Reference includes a lever mechanism, which is mounted on the hand to abut with a semiconductor wafer, and an operation member for operating the lever mechanism which is mounted on an arm that holds the hand turnably. Further, the operation member is disposed at an eccentric position with respect to a turning center of the hand.
However, in the clamp mechanism described in the above-mentioned Patent Reference, the operation member is disposed at the eccentric position with respect to the turning center of the hand and thus the size of the clamp mechanism is increased in a radial direction. Therefore, in the industrial robot described in the Patent Reference, it is difficult to reduce the size in the radial direction of a connecting portion of the arm with the hand and, as a result, downsizing of the industrial robot becomes difficult.